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1/****************************************************************************
2 * Nagios run command utilities
3 *
4 * License: GPL
5 * Copyright (c) 2005 nagios-plugins team
6 *
7 * $Id: utils_cmd.c 1434 2006-06-18 19:36:48Z opensides $
8 *
9 * Description :
10 *
11 * A simple interface to executing programs from other programs, using an
12 * optimized and safe popen()-like implementation. It is considered safe
13 * in that no shell needs to be spawned and the environment passed to the
14 * execve()'d program is essentially empty.
15 *
16 *
17 * The code in this file is a derivative of popen.c which in turn was taken
18 * from "Advanced Programming for the Unix Environment" by W. Richard Stevens.
19 *
20 * Care has been taken to make sure the functions are async-safe. The one
21 * function which isn't is cmd_init() which it doesn't make sense to
22 * call twice anyway, so the api as a whole should be considered async-safe.
23 *
24 * License Information:
25 *
26 * This program is free software; you can redistribute it and/or modify
27 * it under the terms of the GNU General Public License as published by
28 * the Free Software Foundation; either version 2 of the License, or
29 * (at your option) any later version.
30 *
31 * This program is distributed in the hope that it will be useful,
32 * but WITHOUT ANY WARRANTY; without even the implied warranty of
33 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
34 * GNU General Public License for more details.
35 *
36 * You should have received a copy of the GNU General Public License
37 * along with this program; if not, write to the Free Software
38 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
39 */
40
41#define NAGIOSPLUG_API_C 1
42
43/** includes **/
44#include "common.h"
45#include "utils_cmd.h"
46#include "utils_base.h"
47
48#ifdef HAVE_SYS_WAIT_H
49# include <sys/wait.h>
50#endif
51
52/** macros **/
53#ifndef WEXITSTATUS
54# define WEXITSTATUS(stat_val) ((unsigned)(stat_val) >> 8)
55#endif
56
57#ifndef WIFEXITED
58# define WIFEXITED(stat_val) (((stat_val) & 255) == 0)
59#endif
60
61/* 4.3BSD Reno <signal.h> doesn't define SIG_ERR */
62#if defined(SIG_IGN) && !defined(SIG_ERR)
63# define SIG_ERR ((Sigfunc *)-1)
64#endif
65
66/* This variable must be global, since there's no way the caller
67 * can forcibly slay a dead or ungainly running program otherwise.
68 * Multithreading apps and plugins can initialize it (via CMD_INIT)
69 * in an async safe manner PRIOR to calling cmd_run() or cmd_run_array()
70 * for the first time.
71 *
72 * The check for initialized values is atomic and can
73 * occur in any number of threads simultaneously. */
74static pid_t *_cmd_pids = NULL;
75
76/* Try sysconf(_SC_OPEN_MAX) first, as it can be higher than OPEN_MAX.
77 * If that fails and the macro isn't defined, we fall back to an educated
78 * guess. There's no guarantee that our guess is adequate and the program
79 * will die with SIGSEGV if it isn't and the upper boundary is breached. */
80#ifdef _SC_OPEN_MAX
81static long maxfd = 0;
82#elif defined(OPEN_MAX)
83# define maxfd OPEN_MAX
84#else /* sysconf macro unavailable, so guess (may be wildly inaccurate) */
85# define maxfd 256
86#endif
87
88
89/** prototypes **/
90static int _cmd_open (char *const *, int *, int *)
91 __attribute__ ((__nonnull__ (1, 2, 3)));
92
93static int _cmd_fetch_output (int, output *, int)
94 __attribute__ ((__nonnull__ (2)));
95
96static int _cmd_close (int);
97
98/* prototype imported from utils.h */
99extern void die (int, const char *, ...)
100 __attribute__ ((__noreturn__, __format__ (__printf__, 2, 3)));
101
102
103/* this function is NOT async-safe. It is exported so multithreaded
104 * plugins (or other apps) can call it prior to running any commands
105 * through this api and thus achieve async-safeness throughout the api */
106void
107cmd_init (void)
108{
109#ifndef maxfd
110 if (!maxfd && (maxfd = sysconf (_SC_OPEN_MAX)) < 0) {
111 /* possibly log or emit a warning here, since there's no
112 * guarantee that our guess at maxfd will be adequate */
113 maxfd = 256;
114 }
115#endif
116
117 if (!_cmd_pids)
118 _cmd_pids = calloc (maxfd, sizeof (pid_t));
119}
120
121
122/* Start running a command, array style */
123static int
124_cmd_open (char *const *argv, int *pfd, int *pfderr)
125{
126 char *env[2];
127 pid_t pid;
128#ifdef RLIMIT_CORE
129 struct rlimit limit;
130#endif
131
132 int i = 0;
133
134 /* if no command was passed, return with no error */
135 if (argv == NULL)
136 return -1;
137
138 if (!_cmd_pids)
139 CMD_INIT;
140
141 env[0] = strdup ("LC_ALL=C");
142 env[1] = '\0';
143
144 if (pipe (pfd) < 0 || pipe (pfderr) < 0 || (pid = fork ()) < 0)
145 return -1; /* errno set by the failing function */
146
147 /* child runs exceve() and _exit. */
148 if (pid == 0) {
149#ifdef RLIMIT_CORE
150 /* the program we execve shouldn't leave core files */
151 getrlimit (RLIMIT_CORE, &limit);
152 limit.rlim_cur = 0;
153 setrlimit (RLIMIT_CORE, &limit);
154#endif
155 close (pfd[0]);
156 if (pfd[1] != STDOUT_FILENO) {
157 dup2 (pfd[1], STDOUT_FILENO);
158 close (pfd[1]);
159 }
160 close (pfderr[0]);
161 if (pfderr[1] != STDERR_FILENO) {
162 dup2 (pfderr[1], STDERR_FILENO);
163 close (pfderr[1]);
164 }
165
166 /* close all descriptors in _cmd_pids[]
167 * This is executed in a separate address space (pure child),
168 * so we don't have to worry about async safety */
169 for (i = 0; i < maxfd; i++)
170 if (_cmd_pids[i] > 0)
171 close (i);
172
173 execve (argv[0], argv, env);
174 _exit (STATE_UNKNOWN);
175 }
176
177 /* parent picks up execution here */
178 /* close childs descriptors in our address space */
179 close (pfd[1]);
180 close (pfderr[1]);
181
182 /* tag our file's entry in the pid-list and return it */
183 _cmd_pids[pfd[0]] = pid;
184
185 return pfd[0];
186}
187
188static int
189_cmd_close (int fd)
190{
191 int status;
192 pid_t pid;
193
194 /* make sure the provided fd was opened */
195 if (fd < 0 || fd > maxfd || !_cmd_pids || (pid = _cmd_pids[fd]) == 0)
196 return -1;
197
198 _cmd_pids[fd] = 0;
199 if (close (fd) == -1)
200 return -1;
201
202 /* EINTR is ok (sort of), everything else is bad */
203 while (waitpid (pid, &status, 0) < 0)
204 if (errno != EINTR)
205 return -1;
206
207 /* return child's termination status */
208 return (WIFEXITED (status)) ? WEXITSTATUS (status) : -1;
209}
210
211
212static int
213_cmd_fetch_output (int fd, output * op, int flags)
214{
215 size_t len = 0, i = 0, lineno = 0;
216 size_t rsf = 6, ary_size = 0; /* rsf = right shift factor, dec'ed uncond once */
217 char *buf = NULL;
218 int ret;
219 char tmpbuf[4096];
220
221 op->buf = NULL;
222 op->buflen = 0;
223 while ((ret = read (fd, tmpbuf, sizeof (tmpbuf))) > 0) {
224 len = (size_t) ret;
225 op->buf = realloc (op->buf, op->buflen + len + 1);
226 memcpy (op->buf + op->buflen, tmpbuf, len);
227 op->buflen += len;
228 i++;
229 }
230
231 if (ret < 0) {
232 printf ("read() returned %d: %s\n", ret, strerror (errno));
233 return ret;
234 }
235
236 /* some plugins may want to keep output unbroken, and some commands
237 * will yield no output, so return here for those */
238 if (flags & CMD_NO_ARRAYS || !op->buf || !op->buflen)
239 return op->buflen;
240
241 /* and some may want both */
242 if (flags & CMD_NO_ASSOC) {
243 buf = malloc (op->buflen);
244 memcpy (buf, op->buf, op->buflen);
245 }
246 else
247 buf = op->buf;
248
249 op->line = NULL;
250 op->lens = NULL;
251 i = 0;
252 while (i < op->buflen) {
253 /* make sure we have enough memory */
254 if (lineno >= ary_size) {
255 /* ary_size must never be zero */
256 do {
257 ary_size = op->buflen >> --rsf;
258 } while (!ary_size);
259
260 op->line = realloc (op->line, ary_size * sizeof (char *));
261 op->lens = realloc (op->lens, ary_size * sizeof (size_t));
262 }
263
264 /* set the pointer to the string */
265 op->line[lineno] = &buf[i];
266
267 /* hop to next newline or end of buffer */
268 while (buf[i] != '\n' && i < op->buflen)
269 i++;
270 buf[i] = '\0';
271
272 /* calculate the string length using pointer difference */
273 op->lens[lineno] = (size_t) & buf[i] - (size_t) op->line[lineno];
274
275 lineno++;
276 i++;
277 }
278
279 return lineno;
280}
281
282
283int
284cmd_run (const char *cmdstring, output * out, output * err, int flags)
285{
286 int fd, pfd_out[2], pfd_err[2];
287 int i = 0, argc;
288 size_t cmdlen;
289 char **argv = NULL;
290 char *cmd = NULL;
291 char *str = NULL;
292
293 if (cmdstring == NULL)
294 return -1;
295
296 /* initialize the structs */
297 if (out)
298 memset (out, 0, sizeof (output));
299 if (err)
300 memset (err, 0, sizeof (output));
301
302 /* make copy of command string so strtok() doesn't silently modify it */
303 /* (the calling program may want to access it later) */
304 cmdlen = strlen (cmdstring);
305 if ((cmd = malloc (cmdlen + 1)) == NULL)
306 return -1;
307 memcpy (cmd, cmdstring, cmdlen);
308 cmd[cmdlen] = '\0';
309
310 /* This is not a shell, so we don't handle "???" */
311 if (strstr (cmdstring, "\"")) return -1;
312
313 /* allow single quotes, but only if non-whitesapce doesn't occur on both sides */
314 if (strstr (cmdstring, " ' ") || strstr (cmdstring, "'''"))
315 return -1;
316
317 /* each arg must be whitespace-separated, so args can be a maximum
318 * of (len / 2) + 1. We add 1 extra to the mix for NULL termination */
319 argc = (cmdlen >> 1) + 2;
320 argv = calloc (sizeof (char *), argc);
321
322 if (argv == NULL) {
323 printf ("%s\n", _("Could not malloc argv array in popen()"));
324 return -1;
325 }
326
327 /* get command arguments (stupidly, but fairly quickly) */
328 while (cmd) {
329 str = cmd;
330 str += strspn (str, " \t\r\n"); /* trim any leading whitespace */
331
332 if (strstr (str, "'") == str) { /* handle SIMPLE quoted strings */
333 str++;
334 if (!strstr (str, "'"))
335 return -1; /* balanced? */
336 cmd = 1 + strstr (str, "'");
337 str[strcspn (str, "'")] = 0;
338 }
339 else {
340 if (strpbrk (str, " \t\r\n")) {
341 cmd = 1 + strpbrk (str, " \t\r\n");
342 str[strcspn (str, " \t\r\n")] = 0;
343 }
344 else {
345 cmd = NULL;
346 }
347 }
348
349 if (cmd && strlen (cmd) == strspn (cmd, " \t\r\n"))
350 cmd = NULL;
351
352 argv[i++] = str;
353 }
354
355 return cmd_run_array (argv, out, err, flags);
356}
357
358int
359cmd_run_array (char *const *argv, output * out, output * err, int flags)
360{
361 int fd, pfd_out[2], pfd_err[2];
362
363 /* initialize the structs */
364 if (out)
365 memset (out, 0, sizeof (output));
366 if (err)
367 memset (err, 0, sizeof (output));
368
369 if ((fd = _cmd_open (argv, pfd_out, pfd_err)) == -1)
370 die (STATE_UNKNOWN, _("Could not open pipe: %s\n"), argv[0]);
371
372 if (out)
373 out->lines = _cmd_fetch_output (pfd_out[0], out, flags);
374 if (err)
375 err->lines = _cmd_fetch_output (pfd_err[0], err, flags);
376
377 return _cmd_close (fd);
378}